1. Field of the invention
The present invention relates to a food product containing a thrombolytic enzyme, nattokinase, but containing little or none of a blood coagulation factor, vitamin K2.
2. Description of the Prior Art
The Bacillus natto was discovered by Sumi et al. to produce the thrombolytic enzyme nattokinase (Experientia Vol. 43, p. 1110 (1987)), and thus the nutritional value of natto and its value as a health food are looked at again. It is known that nattokinase itself acts as a fibrinolytic enzyme, and lyses thrombi when ingested as a food. Nattokinase has extremely good characteristics such as having a long half life and retaining its effectiveness for a long period of time. In addition, it is reported that urokinase having the same thrombolytic activity as nattokinase does not clearly have a therapeutic effect on incipient central retinal vein occlusion, but that this effect can be clearly seen with nattokinase (Nishimura et al., Ganka Rinsho Ihou (in Japanese), Vol. 88, No. 9, pp. 53-57 (1994)).
Accordingly, food products containing large amounts of nattokinase, for example, powders and capsules formed from Bacillus natto culture extract, are being marketed as health foods.
On the other hand, the Bacillus natto is known to produce large amounts of vitamin K2. Vitamin K2 is known as an essential component of the blood coagulation system. Further, vitamin K2 has other physiological functions, and is said to cause absorption disorders in newborns and osteoporosis in the elderly when it is deficient, and said to cause hemolytic anemia, splenomegaly, nephropathy, hepatopathy and the like when it is present in excess. Thus, a Bacillus natto culture extract simultaneously contains nattokinase as a thrombolytic system effector and vitamin K2 as a blood coagulation system effector.
The necessary daily intake of vitamin K2 for adults is generally 55 to 65 μg. Large amounts of vitamin K's are found in foods such as seaweed, broccoli and the like. Because vitamin K's are also produced by enterobacteria and by Bacillus natto that grow in the intestines when natto is ingested, it is possible for vitamin K2 to be produced. Therefore, it is said that the necessary intake of vitamin K2 can be satisfied by a normal diet. Thus, it is generally not necessary to supplement vitamin K2.
On the other hand, problems occur with patients who are administering synthetic inhibitors of the vitamin K-dependent blood coagulation factors (for example, protothrombin VII, IX, X and the like) to prevent thrombosis. When these patients ingest a natto or a Bacillus natto culture extract containing the thrombolytic enzyme, nattokinase, in order to prevent thrombosis and the like, they also ingest vitamin K2 at the same time, and the effect of synthetic inhibitor of the vitamin K-dependent blood coagulation factor is counteracted.
Accordingly, in order to prevent thrombogenesis, a food product of Bacillus natto culture extract in which the vitamin K2 content has been reduced are desired, and therefore, methods of reducing vitamin K2 in the food product have been attempted. Using organic solvents such as hexane to extract fat-soluble vitamin K2 is one of these methods.
However, the problems with this method are: fat-soluble nutrients are also extracted and removed in addition to vitamin K2: the need to remove organic solvents such as hexane leads to problems in terms of a production technique such as an increase in the cost of production; consumer opposition to the use of organic solvents; and the possibility that organic solvents remain in the food.
Accordingly, a Bacillus natto culture extract in which the vitamin K2 content has been reduced is in demand, as well as a method in which vitamin K2 can be simply and easily extracted without using organic solvents.